WO2016019756A1

WO2016019756A1 - Distributed surface acoustic wave resonator and surface acoustic wave sensing system

Info

Publication number: WO2016019756A1
Application number: PCT/CN2015/081119
Authority: WO
Inventors: 董兰飞; 滕学志; 陈海军; 韦江波; 佟强
Original assignee: 软控股份有限公司
Priority date: 2014-08-02
Filing date: 2015-06-10
Publication date: 2016-02-11
Also published as: EP3176949A4; EP3176949B1; EP3176949A1; CN105322912A; CN105322912B

Abstract

Disclosed are a distributed surface acoustic wave resonator and a surface acoustic wave sensing system. The distributed surface acoustic wave resonator comprises a first antenna (101), a matching network (102), a reflecting grating (103) and an interdigital transducer (104). At least the reflecting grating (103) and the interdigital transducer (104) are provided on a piezoelectric substrate (105). The matching network (102) comprises a best-matching network consisting of at least one capacitor and at least one inductor. The best-matching network is further connected in parallel to a switch circuit. The switch circuit comprises several branch circuits connected with each other in parallel. Each of the branch circuits is provided with at least one capacitor and/or inductor. Each branch circuit of the switch circuit is also provided with a switch used for controlling a conducting state of the branch circuit. By means of the distributed surface acoustic wave resonator, when the matching network accesses different branch circuits, the corresponding resonator corresponds to a centre frequency. By controlling the change in an accessed branch circuit, the centre frequency of the resonator can be changed. The circuit is simple in structure and occupies a small space.

Description

Distributed surface acoustic wave resonator and surface acoustic wave sensing system

Technical field

The present invention relates to a surface acoustic wave sensor, and more particularly to a distributed surface acoustic wave resonator.

Background technique

Radio Frequency Identification (RFID) is a technology that uses contactless tags to automatically identify target objects and acquire relevant data through RF signals. Single-port surface acoustic wave (SAW) resonators are an important part of RFID products, including interdigital transducers (IDTs) and reflective grids. Reflective grids are used to form an acoustic resonator. The device is used for mutual conversion of sound and electricity.

The surface acoustic wave excited by the IDT on the surface of the substrate is reflected and superimposed back and forth between the reflective gratings. When the external signal excitation frequency f is equal to the center frequency f0 of the SAW resonator, a standing wave is formed in the resonant cavity to resonate, and the resonant frequency f0 is SAW. The important characteristic parameters of the resonator, the external perturbation change (such as the change of the reactance value of the matching network) will bring about the change of the output center frequency f0, and the change of the center frequency f0 directly reflects the measured information.

In the distributed surface acoustic wave passive wireless temperature sensing system, which are used to measure different parameters, respectively, the center frequencies are different from each other, in order to prevent the frequency interference from occurring at the center frequency. However, a sensor having a plurality of center frequencies has a problem that the sensor structure is complicated and the manufacturing cost is high.

The Chinese patent application of the patent publication No. CN101877073A relates to a field-programmable surface acoustic wave radio frequency electronic tag, wherein each surface of the reflective surface strip of the surface acoustic wave electronic tag is provided with contacts, and these distributed reflections The surface acoustic wave electronic tags are further connected to each other; the surface acoustic wave electronic tag further comprises an integrated circuit chip having a switching function disposed thereon, the external contact point of the integrated circuit chip and the reflective grid array of the surface acoustic wave electronic tag One-to-one correspondence is set, and the open circuit and short circuit connection between any two contacts of the distributed reflection grid array is controlled by field programming control switch circuit. The invention combines with the existing integrated circuit design, and utilizes the switching array implemented by the existing integrated circuit to change each of the reflective grating arrays. The open circuit and short circuit of the reflective grating strip realize the field programmable of the surface acoustic wave radio frequency electronic tag, and enhance the versatility and flexibility of the design. However, the surface acoustic wave radio frequency electronic tag of the structure has the following disadvantages: 1. By placing the integrated circuit chip on the reflective grid, one reflective gate can only monitor one center frequency value, when multiple center frequency values need to be monitored, It is necessary to provide a plurality of reflective grids, and corresponding piezoelectric substrates requiring a larger area are used for mounting the reflective grid, which increases the manufacturing cost of the sensor on the one hand, and increases the volume of the sensor on the other hand, and is not suitable for miniaturization of the product on the market. demand. 2. Since the reflection of sound waves between the reflection grids has energy loss, when multiple reflection grids are provided, the energy loss of the sound waves transmitted to the last reflection grid will be large, the corresponding sensitivity and reliability will be reduced, and the signals will suffer. After a large energy loss, the transmission distance is also shortened accordingly.

Summary of the invention

In order to solve the technical problem that the existing surface acoustic wave sensor occupies a large volume, the present invention provides a surface acoustic wave resonator type vibration sensor.

In order to solve the above technical problem, the present invention is implemented by the following technical solutions:

A distributed surface acoustic wave resonator comprising a first antenna, a matching network, a reflective grid, and an interdigital transducer, the at least reflective grid, and the interdigital transducer being disposed on a piezoelectric substrate, the matching The network includes a best matching network consisting of at least one capacitor and at least one inductor, the best matching network also having a switching circuit in parallel, the switching circuit comprising a plurality of parallel branches, each branch having at least one Capacitor and/or inductive devices, each of the branches of the switching circuit is also provided with a switch for controlling the conduction state of the branch.

Further, the switch circuit is a field programmable control switch circuit, and the switches of each branch of the switch circuit are controlled by a field programming control logic device.

Further, the field programming control logic device includes n sets of external contact points, and each set of the field programming control switch circuit has a set of external contact points connected in series, and the field programming control logic device controls each group through programming. The conduction state of the outer contact point, where n is not less than the number of branches included in the switching circuit.

Further, the distributed surface acoustic wave resonator corresponds to at most 2 ⁿ center frequencies.

Wherein, the best matching network is composed of a first capacitor (C1) and a first inductor (L1) connected in series, and the field programming control switch circuit is connected in parallel at both ends of the series circuit composed of the best matching network.

Alternatively, the best matching network is composed of a first capacitor (C1) and a first inductor (L1) connected in series, and the field programming control switch circuit is connected in parallel at both ends of the first inductor (L1).

Moreover, the best matching network is composed of a first capacitor (C1) and a first inductor (L1) connected in series, and the field programming control switch circuit is connected in parallel at both ends of the first capacitor (C1).

Based on the above-described distributed surface acoustic wave resonator, the present invention also provides a distributed surface acoustic wave passive wireless sensing system, comprising a reader and a signal processing module, wherein the reader is provided with a second antenna Also included is a distributed surface acoustic wave resonator according to any one of claims 1-7.

Compared with the prior art, the advantages and positive effects of the present invention are: a distributed surface acoustic wave resonator of the present invention, by providing a switching circuit in a matching network, the switching circuit comprising a plurality of parallel branches At least one capacitor and/or inductor device is disposed on each branch. When the matching network accesses different branches, the corresponding resonator corresponds to a center frequency, and the access branch can be changed by controlling to change the resonator. The center frequency, the circuit is easy to implement, the circuit structure is simple, the space is small, and the area of the piezoelectric substrate is not required to be increased, which is advantageous for cost saving.

Other features and advantages of the present invention will become more apparent from the detailed description of the embodiments.

DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the description of the prior art will be briefly described below. Obviously, the drawings in the following description are only It is a certain embodiment of the present invention, and other drawings can be obtained from those skilled in the art without any creative work.

1 is a schematic structural view of an embodiment of a distributed surface acoustic wave resonator proposed by the present invention;

2 is a schematic block diagram of a matching network of the distributed surface acoustic wave resonator of FIG. 1;

3 is a circuit schematic diagram of the matching network of FIG. 2;

4 is an equivalent circuit diagram of the matching network circuit of FIG. 3;

Figure 5 is a model diagram of an equivalent circuit of a resonator in the third embodiment;

Figure 6 is a graph showing the relationship between the reflectance of the resonator and the frequency in the fourth embodiment;

7 is a schematic diagram of an embodiment of a distributed surface acoustic wave passive wireless sensing system according to the present invention. block diagram.

detailed description

The technical solutions in the embodiments of the present invention are clearly and completely described in the following with reference to the accompanying drawings in the embodiments of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention.

Embodiment 1, as shown in FIG. 1 , this embodiment provides a distributed surface acoustic wave resonator, including an antenna 101 , a matching network 102 , a reflective gate 103 , and an interdigital transducer 104 , at least a reflective gate 103 , And the interdigital transducer 104 is disposed on the piezoelectric substrate 105. As shown in FIG. 2, the matching network 102 includes a best matching network composed of at least one capacitor and at least one inductor. The best matching network is also connected in parallel with a switch. a circuit, the switch circuit includes a plurality of parallel branches, each branch is provided with at least one capacitor and/or an inductive device, and each branch of the switch circuit is further provided with a branch for controlling the conduction state of the branch. switch. The working principle of the distributed surface acoustic wave resonator of this embodiment is that the antenna 101 receives the excitation signal. In this embodiment, a switching circuit is added to the matching network, and the center frequency of the resonator can be changed by controlling the branch of the access. In turn, the matching center is connected to the center frequency of the interdigital transducer signal, and a resonator can be flexibly set to change its center frequency. In the distributed surface acoustic wave passive wireless temperature sensing system, respectively, for measurement Different parameters avoid the problem of frequency interference caused by the center frequency, the circuit is easy to implement, the circuit structure is simple, the space is small, and the area of the piezoelectric substrate is not required to be increased, which is beneficial to cost saving. It should be noted that the reactance components disposed on each branch can be respectively a capacitor or an inductor, or a combination of a capacitor and an inductor. The number of the components of the reactance component can be combined at will, so that when the branch is incorporated, The center frequency value of the matching network can be changed. The distributed surface acoustic wave resonator in this embodiment may be a single port resonator or a dual port resonator.

Embodiment 2, this embodiment provides a preferred circuit of a distributed surface acoustic wave resonator, wherein the switch circuit adopts a field programming control switch circuit, as shown in FIG. 3, each branch of the switch circuit The switch accepts control of the field programming control logic device P1.

As a preferred embodiment, the field programming control logic device P1 includes n sets of external contact points. In the present embodiment, FIG. 3 shows three sets of external contact points, respectively (M1, M2), (N1, N2), ( Q1, Q2), the three sets of contacts are respectively connected to the three branches of the switch circuit, that is, each of the switch circuits A set of external contact points are connected in series in the branch, and the field programming control logic device P1 controls the conduction state of the external contact points of each group by programming, for example, when the field programming control logic device P1 controls (M1, M2) is turned on, The capacitor C2 of the branch is connected to the matching network, and the access branch is controlled by the field programming control logic device P1, thereby changing the reactance value of the matching network, thereby changing the center frequency of the matching network, where n is not less than the switching circuit. The number of branches included. This embodiment uses the field programming control logic device P1 for semi-customized, fully custom circuit design. Field-programmable logic devices (PLDs) include not only simpler PROM, EPROM, EEPROM, but also intermediate and advanced PLA, PAL, GAL, EPLD, CPLD, FPGA and many other forms. The field programmable logic device that meets the user's design requirements has the advantages of low power consumption, high speed, miniaturization, multi-function, low cost, flexible design, and unlimited field programming. They can record write data, control the characteristics of each port, and achieve electrical connection and disconnection between ports.

The number of branches n of the switching circuit is not limited to the example of the embodiment, and the field programming control logic device P1 controls to change the conduction state of the external contact point. Theoretically, the distributed surface acoustic wave resonator corresponds to a maximum of 2 ⁿ center frequencies. The great function expansion of the distributed surface acoustic wave resonator can realize the detection center frequency of a plurality of central resonators only by adding a field programming control logic device P1 in the matching network, and thus can theoretically detect a plurality of types. Physical parameters, and the center frequency between the resonators does not affect each other.

In this embodiment, the best matching network is composed of a first capacitor C1 and a first inductor L1 connected in series, and the field programming control switch circuit shown in FIG. 3 is connected in parallel at both ends of the series circuit composed of the best matching network. . The switching circuit and the best matching network together form a T-type matching network or a PI-type matching network.

Alternatively, the best matching network is composed of a first capacitor C1 and a first inductor L1 connected in series, and the field programming control switch circuit is connected in parallel at both ends of the first inductor L1.

Moreover, the best matching network is composed of a first capacitor C1 and a first inductor L1 connected in series, and the field programming control switch circuit is connected in parallel at both ends of the first capacitor C1. The above two solutions are not shown in the figure. For the modification of the first solution, those skilled in the art can deduce the first solution without any creative work, and no further details are provided herein.

Embodiment 3, this embodiment illustrates the basic principle of the distributed surface acoustic wave resonator in the second embodiment. Since each branch has a capacitor and/or an inductor connected in series, no matter any branch is newly connected to the matching network, Both will change the reactance value of the matching network. This embodiment gives another way of incorporation, see Figure 4. It is shown that the equivalent capacitive reactance of the matching network is C', the equivalent inductance is L', and the calculation method of the impedance value Zeq2 of the matching network is:

w=2×π×f (2)

The equivalent circuit model of the universal near resonator of the resonator is shown in Fig. 5. In Fig. 5, C and L are the dynamic capacitance and inductance respectively due to the elasticity and inertia of the piezoelectric substrate, and R is the dynamic resistance caused by the damping, C0 is The static capacitance of the interdigital transducer, R0 is the lead resistance. The equivalent circuit parameters of the resonator include five parameters R0, R, L, C, and C0.

The calculation method of the impedance of the resonator is Zeq1:

Zeq is the equivalent impedance of the structure composed of the resonator Zeq1 and the matching network Zeq2, that is, the total impedance value of the entire structure, therefore,

Zeq=Zeq1+Zeq2 (4)

In general, the characteristic impedance of a common transmission line is 50Ω, and the matching point corresponds to the center frequency of S11, that is, the frequency with the smallest amplitude, and the reflection coefficient is:

A relationship diagram between S11 and frequency f can be obtained from the equations (1 to 5), and the frequency f0 having the smallest amplitude corresponds to the center frequency of S11. In the matching network, the integration of the capacitance or inductance in the external sensor will cause the equivalent value of C1 or L1 to change, affecting the value of Zeq2, and finally affecting the graph of S11. The frequency f0 with the smallest amplitude is the entire resonator structure. The center frequency will change accordingly, and the frequency f0 with the smallest amplitude will change correspondingly to the center frequency of the entire resonator structure.

Embodiment 4 This embodiment shows a specific structure of a distributed surface acoustic wave resonator in which a piezoelectric substrate is a 0.35 mm thick ST quartz wafer. The resonant frequency of the resonator is selected in the ISM band of 433.92 MHz, and the finger width is 3.68 μm, which means that the duty ratio is set to 0.5.

The interdigital transducer has a film thickness of 2,500 angstroms, a wavelength of 7.19 micrometers, and an acoustic aperture of 358 micrometers. Yes, the number of reflective grid bars is 200 pairs, and the interdigital transducer fingers are separated from the reflective grid fingers by a width of 1.79 microns. Resonator equivalent circuit parameter lead resistance R0 is 5 ohms, dynamic resistance R caused by damping is 63.3 ohms, dynamic inductance L caused by piezoelectric substrate elasticity and inertia is 4.511×105nH, dynamics caused by piezoelectric substrate elasticity and inertia Capacitor C is 2.983×10-7nF, and the static capacitance C0 of the interdigital transducer is 7.0×10-4nF. When C1=1.2pF and L1=96.1nH are the best matching network, L2 is 20nH and L3 is 85nH. L4 is 92nH. If the field programming control logic device P1 branch control bit has 3 bits, the conduction state of each branch is shown from left to right, respectively: 000 means that each contact is disconnected, and the resonator center frequency is 433.90. MHz, 100 means that the connection contacts (M1, M2) are turned on, the resonator center frequency is 433.84 MHz; 010 means that the contacts (N1, N2) are turned on, the resonator center frequency is 433.86 MHz; 001 means the contacts (Q1, Q2) Conduction, at this time, the center frequency of the resonator is 433.88MHz; in addition, it can be additionally calculated that when the P1 code of the field programming control logic device is 101, the center frequency of the resonator is 433.82MHz; when the code is 110, the center frequency of the resonator For 433.81MHz, the relationship between the reflectivity of the resonator S11 and the frequency is as shown in Fig. 6. See centers different frequencies and, correspondingly, will not interfere.

Embodiment 5, based on a distributed surface acoustic wave resonator according to Embodiments 1 to 3, the embodiment provides a distributed surface acoustic wave passive wireless sensing system, as shown in FIG. 7, including a reader, a signal processing module, the reader is provided with a second antenna 201, and the vibration sensor is provided with a first antenna 101, and the two are communicated. Referring to FIG. 2, the vibration sensor further includes a matching network 102 and a reflection grid. 103, and an interdigital transducer 104, at least a reflective grid 103, and an interdigital transducer 104 are disposed on the piezoelectric substrate 105. As shown in FIG. 3, the matching network 102 includes at least one capacitor C1 and at least one inductor. a best matching network composed of L1, the best matching network also has a switching circuit in parallel, the switching circuit comprises a plurality of parallel branches, each branch is provided with at least one capacitor and / or inductance device, the switching circuit A switch for controlling the conduction state of the branch is also provided on each branch. The working principle of the wave passive wireless sensing system of this embodiment is that the reader sends an excitation signal to the vibration sensor through the second antenna 201, and the vibration sensor receives the excitation signal through the first antenna 101, and the vibration sensor adds a switching circuit on the matching network. By controlling the branch of the access change, the center frequency of the resonator can be changed, thereby changing the center frequency of the matching network to the interdigital transducer signal, so that a resonator can be flexibly set to change its center frequency.

Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the above examples. Variations, modifications, additions or substitutions made by those skilled in the art within the scope of the invention are also intended to be within the scope of the invention.

Claims

A distributed surface acoustic wave resonator comprising a first antenna, a matching network, a reflective grid, and an interdigital transducer, the at least reflective grid, and the interdigital transducer being disposed on the piezoelectric substrate, wherein The matching network includes a best matching network composed of at least one capacitor and at least one inductor. The best matching network is further connected with a switching circuit. The switching circuit includes a plurality of parallel branches, each of the branches. At least one capacitor and/or inductive component is provided, and each branch of the switching circuit is further provided with a switch for controlling the conduction state of the branch.
The distributed surface acoustic wave resonator of claim 1 wherein said switching circuit is a field programmed control switching circuit, and wherein the switches of each branch of said switching circuit are controlled by a field programming control logic device.
The distributed surface acoustic wave resonator according to claim 2, wherein said field programming control logic device comprises n sets of external contact points, and each set of said field programming control switch circuit is connected in series An external contact point, the field programming control logic device controls the conduction state of each set of external contact points by programming, wherein n is not less than the number of branches included in the switching circuit.
The distributed surface acoustic wave resonator according to claim 3, wherein said distributed surface acoustic wave resonator corresponds to at most 2 n center frequencies.
The distributed surface acoustic wave resonator according to any one of claims 1 to 4, wherein the optimal matching network is composed of a first capacitor (C1) and a first inductor (L1) connected in series, The field programming control switch circuit is connected in parallel across the series circuit of the best matching network.
The distributed surface acoustic wave resonator according to any one of claims 1 to 4, wherein the optimal matching network is composed of a first capacitor (C1) and a first inductor (L1) connected in series, The field programming control switch circuit is connected in parallel at both ends of the first inductor (L1).
The distributed surface acoustic wave resonator according to any one of claims 1 to 4, wherein the optimal matching network is composed of a first capacitor (C1) and a first inductor (L1) connected in series, The field programming control switch circuit is connected in parallel at both ends of the first capacitor (C1).
A surface acoustic wave sensing system, comprising: a reader, a signal processing module, the reader being provided with a second antenna, and further comprising the distributed according to any one of claims 1-7 Surface acoustic wave resonators.